Graphene is a two-dimensional monolayer of sp2-bonded carbon atoms that has been attracting great interest following its experimental isolation by the mechanical cleavage of graphite. Its unique physical properties, such as high intrinsic carrier mobility (˜200,000 cm2/Vs), quantum electronic transport, tunable band gap, high mechanical strength and elasticity, and superior thermal conductivity, make graphene promising for many applications, including high speed transistors, energy/thermal management, and chemical/biological sensors. As the current generation of silicon-based devices reach their fundamental minimum size limit in the coming years, graphene will provide an opportunity to design even smaller devices. Since graphene remains conductive and stable at the molecular level, it is in a position to provide the next generation of low power electronics.
Since the first isolation of graphene by mechanical exfoliation, various methods have been devised to produce graphene. So far, graphene with the best electronic properties has been synthesized by mechanical exfoliation from Highly Ordered Pyrolytic Graphite (HOPG), which is on the order of tens of micrometers in size. Graphene can also be produced by chemical reduction of graphite oxide, high temperature annealing of single crystal silicon carbide, and chemical vapor deposition (CVD) on metal substrates. These techniques have been employed in demonstrating good quality graphene transistors. However, the only one that has the promise of becoming an inexpensive and manufacturable technology for deposition of reasonably high quality graphene is CVD, which has been one of the most-used thin film fabrication techniques in silicon very-large-scale integration (VLSI). The method mainly involves the adsorption, decomposition and segregation of a carbon-containing precursor on transition metal surface at an elevated temperature either at low or atmospheric pressure, which results in graphene synthesis. In particular, recent developments on uniform single layer deposition of graphene on copper foils over large areas have allowed access to high quality material. However, for the outstanding properties of graphene to be fully utilized, the synthesized graphene must be able to be transferred from the formation substrate to a variety of other target substrates. Particularly, in order for electrical current to flow through graphene devices as opposed to being shorted out by a conducting substrate, graphene must be removed from the conducting catalyst surface and transferred onto an insulating surface. While a number of processes have been developed to aid in this transfer, there currently remains an unmet need for improved processes to effectively and efficiently transfer graphene to target substrates.